THURSDAY, May 21 (HealthDay News) -- More pregnant women in drug treatment programs are there due to methamphetamine use than any other drug, new research shows.

The number of expectant mothers seeking treatment for methamphetamine abuse tripled from 1994 to 2006. In 1994, methamphetamine use accounted for 8 percent of all admissions for pregnant women, but by 2006 that number was 24 percent, the researchers report.

"Methamphetamine is the primary drug that compels treatment admission. It's the most common drug, including alcohol," said study author Dr. Mishka Terplan, an assistant professor of obstetrics and gynecology at the University of Chicago Medical Center.

Results of the study are published in the June issue of Obstetrics & Gynecology.

Methamphetamine is a stimulant that's highly addictive. It can be taken orally, snorted, injected or smoked, according to the U.S. National Institute on Drug Abuse (NIDA). Treatments aimed at changing behaviors tend to be the most effective for helping people beat a methamphetamine addiction, according to NIDA.

About 731,000 Americans over age 12 are estimated to currently use methamphetamine, according to NIDA. In 2006, over 400,000 women of reproductive age reported using methamphetamine, according to background information in the study.

It's not clear what effects methamphetamine use has on fetal development, or if there are any long-term effects on children exposed in utero. One study, according to Terplan, found that babies born to mothers using methamphetamine may be slightly smaller. However, a recent study published in Neurology suggests that methamphetamine exposure may cause microscopic structural changes in children's brains. What isn't known from this study is what the long-term impact of such changes might be, if there is any impact.

For the current study, Terplan and his colleagues reviewed data from the Treatment Episode Data Set, which details admissions to federally funded treatment centers.

In 1994, the number of pregnant women admitted to federally funded treatment centers was 18,034, but by 2006, the number increased to 22,382 expectant mothers seeking treatment for drug and alcohol abuse. During that time period, alcohol and cocaine use declined as the primary substance of abuse, while methamphetamine and marijuana use increased.

At the beginning of the study, 1,457 pregnant women said that amphetamines or methamphetamine was their primary drug of abuse. In 2006, that number jumped to 5,312 pregnant women, the study authors note.

The study also found the percentage of methamphetamine use among expectant mothers seeking treatment (24 percent) was higher than for men (7 percent) or for nonpregnant women (12 percent). Additionally, the researchers reported that most methamphetamine admissions in pregnant women occurred in the West, among white women and in unemployed women. In 2006, women also reported having more psychiatric disorders and being more marginalized in society.

"Most women decrease or stop using during pregnancy," said Terplan. "But, they're aware of the stigma associated with abuse behavior and they may be reluctant to seek care. They may also have concerns about losing their children. We really need to provide clinical environments in which women are comfortable disclosing their use and we need to have referral resources. Pregnancy is an opportunity to intervene not only in maternal health, but in the family's health."

David Deitch, senior vice president and chief clinical officer of the Phoenix House drug treatment centers, said that although methamphetamine use may be somewhat higher in certain areas right now, the challenges that pregnant women who abuse drugs face are the same no matter what the drug.

"Women who are pregnant or have young children are reluctant to enter formal treatment because they must separate from their children, and many treatment programs are reluctant to accept pregnant women," he said.

Both Terplan and Deitch said that what isn't helpful is dragging these women through the criminal justice system, as occurred in the late 1980s and early 1990s when some studies suggested that babies born to women who smoked crack would have devastating health consequences from their mothers' drug abuse.

"What we need is a public health intervention because there are not enough mother and child treatment programs available," said Deitch.

SOURCES: Mishka Terplan, M.D., M.P.H., assistant professor, obstetrics and gynecology, University of Chicago Medical Center; David Deitch, Ph.D., senior vice president and chief clinical officer, Phoenix House, and professor of clinical psychiatry at the University of California, San Diego; June 2009 Obstetrics & Gynecology